As you can see, pattern matching goes great with recursion! Most imperative languages don’t have pattern matching so you have to make a lot of if else statements to test for edge conditions. Here, we simply put them out as patterns. So the first edge condition says that if the list is empty, crash! Makes sense because what’s the maximum of an empty list? I don’t know. The second pattern also lays out an edge condition. It says that if it’s the singleton list, just give back the only element.

Now the third pattern is where the action happens. We use pattern matching to split a list into a head and a tail. This is a very common idiom when doing recursion with lists, so get used to it. We use a where binding to define maxTail as the maximum of the rest of the list. Then we check if the head is greater than the maximum of the rest of the list. If it is, we return the head. Otherwise, we return the maximum of the rest of the list.

In my Scala examples, I’ll start with a simple one. My maximum function will take a list of integers and will return an integer.